diff --git a/biscuit/apps/chronos/model_extensions.py b/biscuit/apps/chronos/model_extensions.py
index b4a6d4adab7ae78f62e8cbca2d0e7ee5a2da13bf..32055e65292f9f1e60b31a4fc8aedd8d2daf4b82 100644
--- a/biscuit/apps/chronos/model_extensions.py
+++ b/biscuit/apps/chronos/model_extensions.py
@@ -5,14 +5,44 @@ from .models import Lesson, LessonPeriod
 
 @Person.property
 def lessons_as_participant(self):
+    """ Return a `QuerySet` containing all `Lesson`s this person
+    participates in (as student).
+
+    .. note:: Only available when BiscuIT-App-Chronos is installed.
+
+    :Date: 2019-11-07
+    :Authors:
+        - Dominik George <dominik.george@teckids.org>
+    """
+
     return Lesson.objects.filter(groups__members=self)
 
 
 @Person.property
 def lesson_periods_as_participant(self):
+    """ Return a `QuerySet` containing all `LessonPeriod`s this person
+    participates in (as student).
+
+    .. note:: Only available when BiscuIT-App-Chronos is installed.
+
+    :Date: 2019-11-07
+    :Authors:
+        - Dominik George <dominik.george@teckids.org>
+    """
+
     return LessonPeriod.objects.filter(lesson__groups__members=self)
 
 
 @Person.property
 def lesson_periods_as_teacher(self):
+    """ Return a `QuerySet` containing all `Lesson`s this person
+    gives (as teacher).
+
+    .. note:: Only available when BiscuIT-App-Chronos is installed.
+
+    :Date: 2019-11-07
+    :Authors:
+        - Dominik George <dominik.george@teckids.org>
+    """
+
     return LessonPeriod.objects.filter(lesson__teachers=self)